ADAMTS and ADAM metalloproteinases in osteoarthritis - looking beyond the 'usual suspects'.

INTRODUCTION: Matrix metalloproteinases (MMPs) and 'aggrecanase' a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs) are well established to play key roles in osteoarthritis (OA) through degradation of extracellular matrix (ECM) type II collagen and aggrecan, and are thus potential targets for development of OA therapies. OBJECTIVE: This paper aims to provide a comprehensive review of the expression and potential roles of other, lesser-known ADAMTSs and related adamalysins (or a disintegrin and metalloproteinases (ADAMs)) in cartilage, with a view to identifying potentially protective or homeostatic metalloproteinases in the joint and informing consequent selective inhibitor design. DESIGN: A comprehensive literature search was performed using PubMed terms 'osteoarthritis' and 'ADAMTS' or 'ADAM'. RESULTS: Several ADAMTSs and ADAMs were identified as having reportedly increased expression in OA. These include enzymes likely to play roles in cartilage matrix anabolism (e.g., the procollagen N-proteinases ADAMTS-2, ADAMTS-3 and ADAMTS-14), chondrocyte differentiation and proliferation (e.g., ADAM9, ADAM10, ADAM12), as well as enzymes contributing to cartilage catabolism (e.g., Cartilage oligomeric protein (COMP)-degrading ADAMTS-7 and ADAMTS-12). CONCLUSIONS: In addition to the well-characterised MMPs, ADAMTS-4 and ADAMTS-5, many other ADAMTSs and ADAMs are expressed in cartilage and several show significantly altered expression in OA. Studies aimed at elucidating the pathophysiological roles of these enzymes in cartilage will contribute to our understanding of OA pathogenesis and enable design of targeted inhibitors that effectively target metalloproteinase-mediated cartilage degradation while sparing cartilage repair pathways.

Involvement of ADAMTS5 and hyaluronidase in aggrecan degradation and release from OSM-stimulated cartilage.

The relative contribution of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4 and ADAMTS5 to aggrecan degradation under oncostatin M (OSM) stimulation, the role of the ancillary domains of the aggrecanases on their ability to cleave within the chondroitin sulfate (CS)-2 region, the role of hyaluronidases (HYAL) in stimulating aggrecan release in the absence of proteolysis, and the identity of the hyaluronidase involved in OSM-mediated cartilage breakdown were investigated. Bovine articular cartilage explants were cultured in the presence of interleukin-1beta (IL-1beta), tumor necrosis factor alpha (TNFalpha) and/or OSM, or treated with trypsin and/or hyaluronidase. Aggrecan was digested with various domain-truncated isoforms of ADAMTS4 and ADAMTS5. Aggrecan and link protein degradation and release were analyzed by immunoblotting. Aggrecanase and HYAL gene expression were determined. ADAMTS4 was the most inducible aggrecanase upon cytokine stimulation, whereas ADAMTS5 was the most abundant aggrecanase. ADAMTS5 was the most active aggrecanase and was responsible for the generation of an OSM-specific degradation pattern in the CS-2 region. Its ability to cleave at the OSM-specific site adjacent to the aggrecan G3 region was enhanced by truncation of the C-terminal thrombospondin domain, but reduced by further truncation of both the spacer and cysteine-rich domains of the enzyme. OSM has the ability to mediate proteoglycan release through hyaluronan degradation, under conditions where HYAL-2 is the predominant hyaluronidase being expressed. Compared to other catabolic cytokines, OSM exhibits a unique potential at degrading the proteoglycan aggregate, by promoting early robust aggrecanolysis, primarily through the action of ADAMTS5, and hyaluronan degradation.

Interleukin 13 (IL-13)-regulated expression of the chondroprotective metalloproteinase ADAM15 is reduced in aging cartilage.

OBJECTIVE: The adamalysin metalloproteinase 15 (ADAM15) has been shown to protect against development of osteoarthritis in mice. Here, we have investigated factors that control ADAM15 levels in cartilage. DESIGN: Secretomes from wild-type and Adam15 -/- chondrocytes were compared by label-free quantitative mass spectrometry. mRNA was isolated from murine knee joints, either with or without surgical induction of osteoarthritis on male C57BL/6 mice, and the expression of Adam15 and other related genes quantified by RT-qPCR. ADAM15 in human normal and osteoarthritic cartilage was investigated similarly and by fluorescent immunohistochemistry. Cultured HTB94 chondrosarcoma cells were treated with various anabolic and catabolic stimuli, and ADAM15 mRNA and protein levels evaluated. RESULTS: There were no significant differences in the secretomes of chondrocytes from WT and Adam15 -/- cartilage. Expression of ADAM15 was not altered in either human or murine osteoarthritic cartilage relative to disease-free controls. However, expression of ADAM15 was markedly reduced upon aging in both species, to the extent that expression in joints of 18-month-old mice was 45-fold lower than in that 4.5-month-old animals. IL-13 increased expression of ADAM15 in HTB94 â€‹cells by 2.5-fold, while modulators of senescence and autophagy pathways had no effect. Expression of Il13 in the joint was reduced with aging, suggesting this cytokine may control ADAM15 levels in the joint. CONCLUSION: Expression of the chondroprotective metalloproteinase ADAM15 is reduced in aging human and murine joints, possibly due to a concomitant reduction in IL-13 expression. We thus propose IL-13 as a novel factor contributing to increased osteoarthritis risk upon aging.

A trypanosome oligopeptidase as a target for the trypanocidal agents pentamidine, diminazene and suramin.

African trypanosomes contain a cytosolic serine oligopeptidase, called OP-Tb, that is reversibly inhibited by the active principles of three of the five most commonly used trypanocidal drugs: pentamidine, diminazene and suramin. OP-Tb was inhibited by pentamidine in a competitive manner, and by suramin in a partial, non-competitive manner. The inhibition of OP-Tb by a variety of suramin analogues correlated with the trypanocidal efficacy of these analogues (P=0.03; by paired Student's t-test). Since intracellular (therapeutic) concentrations of pentamidine and suramin are reported to reach approximately 206Ki and 15Ki respectively, we suggest that these drugs may exert part of their trypanocidal activity through the inhibition of OP-Tb.

Purification and characterisation of a trypsin-like serine oligopeptidase from Trypanosoma congolense.

Trypanosoma brucei contain a serine oligopeptidase (OP-Tb) that is released into (and remains active in) the blood of trypanosome-infected animals. Here a similar enzyme from Trypanosoma congolense is described. This oligopeptidase, called OP-Tc, was purified using three-phase partitioning, and ion-exchange and affinity chromatography. OP-Tc is inhibited by alkylating agents, by serine peptidase-specific inhibitors including 3,4-dichloroisocoumarin, 4-(2-aminoethyl)benzenesulfonylfluoride and diispropylfluoro-phosphate and by other peptidase inhibitors including leupeptin, antipain and peptidyl chloromethyl ketones. Reducing agents such as dithiothreitol enhanced activity as did heparin, spermine and spermidine. The enzyme has trypsin-like specificity since it cleaved fluorogenic peptides that have basic amino acid residues (Arg or Lys) in the P1 position. Potential substrates without a basic residue in P1 were not hydrolysed. Although OP-Tc has weak arginine aminopeptidase activity, the enzyme clearly preferred substrates that had amino acids in the P2 and P3 positions. Overall, OP-Tc appears to be less efficient than OP-Tb because it usually displayed lower k(cat)/Km values for the substrates tested. However, like OP-Tb, the best substrate for OP-Tc was Cbz-Arg-Arg-AMC (Km = 0.72 microM, k(cat) = 96 s(-1)). OP-Tc preference for amino acids in the P2 position was (Gly,Lys,Arg) > Phe > Leu > Pro. The results also suggest that the P3-binding site has hydrophobic characteristics. OP-Tc may not be a naturally immunodominant molecule because neither IgG nor IgM anti- OP-Tc antibodies were detected in the blood of experimentally infected cattle.

Characterisation of the antitrypanosomal activity of peptidyl alpha-aminoalkyl phosphonate diphenyl esters.

Two groups of irreversible serine peptidase inhibitors, peptidyl chloromethyl ketones and peptidyl phosphonate diphenyl esters, were examined for antitrypanosomal activity against the bloodstream form of Trypanosoma brucei brucei. Both peptidyl chloromethyl ketones and peptidyl phosphonate diphenyl esters inhibited trypsin-like peptidases of the parasites and exhibited antitrypanosomal activity at micromolar concentrations. In live T. b. brucei, labelled analogues of both of these groups of inhibitors primarily targeted an 80-kDa peptidase, possibly a serine oligopeptidase known as oligopeptidase B. In an in vivo mouse model of infection, one of these inhibitors, carbobenzyloxyglycyl-4-amidinophenylglycine phosphonate diphenyl ester, was curative at 5 mg kg(-1) day(-1) but appeared toxic at higher doses. There was no significant correlation between the inhibitory potency (as evaluated against purified T. b. brucei oligopeptidase B) and the in vitro antitrypanosomal efficacy of either group of inhibitors, suggesting that these inhibitors were acting on multiple targets within the parasites, or had different cell permeability properties. These findings suggest that serine peptidases may represent novel chemotherapeutic targets in African trypanosomes.

Production of anti-peptide antibodies against trypanopain-Tb from Trypanosoma brucei brucei: effects of antibodies on enzyme activity against Z-Phe-Arg-AMC.

Anti-peptide antibodies were produced against the cysteine proteinase trypanopain-Tb from Trypanosoma brucei brucei and the effects of these antibodies on enzyme activity against carboxybenzoyl (Z)-Phe-Arg-aminomethylcoumarin (AMC) investigated. A peptide was synthesised corresponding to a region of the trypanopain-Tb active site around the active site histidine so that the resulting anti-peptide antibodies specifically targeted the active site of the enzyme. Such antibodies were considered more likely to modulate enzyme activity compared with antibodies directed against other regions of the enzyme. Trypanopain-Tb activity was modulated by rabbit and chicken antibodies produced against both the free and conjugated peptide. Rabbit anti-peptide antibodies enhanced trypanopain-Tb activity by up to 64% at 500 micrograms/ml relative to non-immune antibodies. Chicken antibodies on the other hand, both enhanced (by up to 176% at 500 mg/ml) and inhibited (by up to 85% at 250 mg/ml) trypanopain-Tb activity against Z-Phe-Arg-AMC. The nature of the antibody effect depended on the stage during the immunisation protocol at which the antibodies were produced. Chicken antibodies also modulated trypanopain-Tb activity in lysates of T.b. brucei, while rabbit antibodies were only effective against the purified enzyme. Anti-trypanopain-Tb peptide antibodies were thus shown to have the potential to affect trypanopain-Tb activity.

Production of cytokines, vascular endothelial growth factor, matrix metalloproteinases, and tissue inhibitor of metalloproteinases 1 by tenosynovium demonstrates its potential for tendon destruction in rheumatoid arthritis.

OBJECTIVE: To investigate the role of proinflammatory cytokines, vascular endothelial growth factor (VEGF), matrix metalloproteinases (MMPs), and tissue inhibitor of metalloproteinases 1 (TIMP-1) in the destruction of tendons by tenosynovium in rheumatoid arthritis (RA). METHODS: Synovial specimens were obtained from encapsulating tenosynovium (n = 17), invasive tenosynovium (n = 13), and wrist joints (n = 17) in 18 RA patients undergoing wrist extensor tenosynovectomy. Synovial membrane cells were dissociated from connective tissue by enzyme digestion and cultured in vitro for 48 hours, and harvested supernatants were assayed for the cytokines tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6), VEGF, MMPs 1, 2, 3, and 13, and TIMP-1 by enzyme-linked immunosorbent assay. Gelatin zymography was performed to demonstrate enzyme activity. Statistical analysis was performed using Student's paired 2-tailed t-tests for parametric data and the Wilcoxon signed rank test for nonparametric data. RESULTS: MMP-1 and MMP-13 levels were approximately 2.5-fold higher in invasive tenosynovium compared with encapsulating tenosynovium. Levels of MMP-2 were approximately 1.5-fold higher in invasive tenosynovium compared with both encapsulating tenosynovium and wrist joint synovium. MMP-13 (P = 0.009) and IL-6 (P = 0.03) levels were significantly lower in encapsulating tenosynovium compared with wrist joint synovium. Levels of VEGF, TIMP-1, TNFalpha, and MMP-3 were similar in all synovial sample groups. Zymography demonstrated enzyme activity in all synovium samples from all 9 patients assessed. CONCLUSION: Tenosynovium produces proinflammatory cytokines and proteolytic enzymes that are important in the tissue degradation seen in RA. Increased production of the enzymes MMP-1, MMP-2, and MMP-13 by invasive tenosynovium suggests a possible explanation for the worse prognosis and increased rupture rate associated with invasive tenosynovitis in RA. Production of VEGF by tenosynovium suggests that angiogenesis may have a role in tenosynovial proliferation and invasion of tendons.

Proteases from Trypanosoma brucei brucei. Purification, characterisation and interactions with host regulatory molecules.

African trypanosomes contain proteases that may be released into the bloodstream of their infected hosts. This paper describes a novel, combined isolation of a cysteine proteinase (called trypanopain-Tb) and a serine oligopeptidase (which we call oligopeptidase-Tb) from Trypanosoma brucei brucei, as well as a comparison of the activities of these two enzymes against several host regulatory molecules. The enzymes differed in various respects. Firstly, purified trypanopain-Tb was shown to readily cleave proteins such as gelatin maximally at acidic pH. In contrast, oligopeptidase-Tb, which is optimally active at alkaline pH, did not hydrolyse proteins larger than 4 kDa. However, it readily hydrolysed various polypeptides, including neurotensin and atrial natriuretic factor. The interaction of the two enzymes with mammalian protease inhibitors also differed. Cystatins and alpha2-macroglobulin effectively inhibited trypanopain-Tb, with the Ki values for cystatin C and low-molecular-mass kininogen (approximately 10(-11) M) predicting, that trypanopain-Tb is likely to be effectively controlled by these inhibitors if released into the host bloodstream. In contrast, oligopeptidase-Tb was not inhibited by serpins or (a2-macroglobulin, suggesting that it may remain active if released into the host bloodstream. In support of these in vitro results, the blood of trypanosome-infected rats displayed no trypanopain-Tb-like activity, but exhibited high oligopeptidase-Tb-like activity. Thus, while trypanopain-Tb seems likely to be confined to an intracellular role within the parasite, oligopeptidase-Tb has the potential to remain active in the host bloodstream and so contribute directly to pathogenesis.

Cysteine proteinase inhibitors kill cultured bloodstream forms of Trypanosoma brucei brucei.

Trypanosoma brucei brucei is a causative agent of bovine trypanosomiasis (nagana), a disease of considerable economic significance in much of Africa. Here we report investigations on the effects of various irreversible cysteine proteinase inhibitors, including vinyl sulfones (VS), peptidyl chloromethylketones (CMK), diazomethylketones, and fluoromethyl ketones, on the major lysosomal cysteine proteinase (trypanopain-Tb) of T. b. brucei and on in vitro-cultured bloodstream forms of the parasite. Many of the tested inhibitors were trypanocidal at low micromolar concentrations. Methylpiperazine urea-Phe-homoPhe-VS was the most effective trypanocidal agent, killing 50% of test populations at a work ing concentration of 0.11 microM, while carbobenzoxy-Phe-Phe-CMK was the most trypanocidal of the methylketones with an IC50 of 3.6 microM. Labelling of live and lysed T. b. brucei with biotinylated inhibitor derivatives suggests that trypanopain-Tb is the likely intracellular target for these inhibitors. Kinetic analysis of the inhibition of purified trypanopain-Tb by the inhibitors showed that most had kass values in the 10(6) M-1 s-1 range. We conclude that cysteine proteinase inhibitors have potential as trypanocidal agents and that a major target of these compounds is the lysosomal enzyme trypanopain-Tb.

Chalcone, acyl hydrazide, and related amides kill cultured Trypanosoma brucei brucei.

BACKGROUND: Protozoan parasites of the genus Trypanosoma cause disease in a wide range of mammalian hosts. Trypanosoma brucei brucei, transmitted by tsetse fly to cattle, causes a disease (Nagana) of great economic importance in parts of Africa. T. b. brucei also serves as a model for related Trypanosoma species, which cause human sleeping sickness. MATERIALS AND METHODS: Chalcone and acyl hydrazide derivatives are known to retard the growth of Plasmodium falciparum in vitro and inhibit the malarial cysteine proteinase, falcipain. We tested the effects of these compounds on the growth of bloodstream forms of T. b. brucei in cell culture and in a murine trypanosomiasis model, and investigated their ability to inhibit trypanopain-Tb, the major cysteine proteinase of T. b. brucei. RESULTS: Several related chalcones, acyl hydrazides, and amides killed cultured bloodstream forms of T. b. brucei, with the most effective compound reducing parasite numbers by 50% relative to control populations at a concentration of 240 nM. The most effective inhibitors protected mice from an otherwise lethal T. b. brucei infection in an in vivo model of acute parasite infection. Many of the compounds also inhibited trypanopain-Tb, with the most effective inhibitor having a Ki value of 27 nM. Ki values for trypanopain-Tb inhibition were up to 50- to 100-fold lower than for inhibition of mammalian cathepsin L, suggesting the possibility of selective inhibition of the parasite enzyme. CONCLUSIONS: Chalcones, acyl hydrazides, and amides show promise as antitrypanosomal chemotherapeutic agents, with trypanopain-Tb possibly being one of their in vivo targets.